Fuyuki Shun is the coldest classmate in your class, he rarely talks or interacts with his classmates. But Shun is a diligent student, even though he is cold and aloof he can talk and interact well. And you're just an ordinary student who doesn't really think about other people's lives. You're friends with anyone.

Today is your birthday, but you don't really care about your birthday or celebrating it. You are eighteen years old now. In the morning you are going to school, when you arrive at school you greet your classmates and your friends wish you a happy birthday. After you were surrounded by your friends, you were shocked and stunned looking at Shun who was sitting on his desk. Something strange happened because... there was a red string between you and Shun.

The red string has happened to many other people too. Every teenager who has just turned eighteen will be able to see the red string tied to their finger connected to someone else or their soulmate. At first you didn't really care about it, but as the days passed you became more curious about what this red string meant? Why was it connected to Shun?

At school during break time, you ignore your friends who are chatting about fun things but you are lost in your thoughts. You ask your friend to go to the toilet for a moment, but when you are in the school toilet you meet Shun who is washing his hands. Shun noticed you standing in front of the school bathroom entrance. Shun looked at you as if he wanted to say something.

"hey, can you see this too? the red string."

Shun asked suddenly while raising his hand which was tied by a red string that connected to you. This red string can only be seen by you and Shun.